Blow striking implement



Jan. 19, 1932. E. BusscHoP ETAL.

BLOW STRIKING IMPLEMENT Filed May 18, 1928 4 Sheets-Sheet l Agra/f2:

Jan. 19, 1932. E- BlssCHop ET AL 1,841,781

BLOW STRIKING IMPLEMENT Filed May 18, 1928 4 shvets-sneet 2 Jan. 19, 1932. E, BlssCHop E1' AL 1,841,781

BLOW STRIKING IMPLEMENT Jan. 19, 1932.

Filed May 18. 1928 4 Sheets-Sheet 4 mf am, mmv WM, 1

WMM.

wmwmhr Patented Jan. 19, 1932 UNITED STATES PATENT ,OFFICE EELCO BISSCHOP, OF BERLIN-SIEMENSSTADT, HILMAR ULBRICH, OF BERLIN-CHAR- LOTTENBURG, AND WILHELM WIRTH, OF BERLIN-SIEMENSSTADT, GERMANY, ASSIGNORS TO' SIEMENS-SCHUKERTWERKE AKTIENGESELLSCHAFT, OF BERLIN- SIEMENSSTADT, GERMANY, A CORPORATION OF GERMANY BLOW s'rnIxING IMPLEMENT Application led May 18, 1928, Serial No. 278,779, and in Germany May 24, 1927."

Our invention relates to improvements in blow-striking implements equipped with a reciprocating hammer head connected with a reciprocating driving member by means of two systems of springs, which transmit the motion of the driving member to the hammer head. Generally the reciprocating or oscillating motion of the driving member is obtained by connecting this member with the revolving shaft of a driving motor by a connecting rod and crank.

Our invention provides means by which the /power of such blow striking implements may be considerably increased.

According to our invention the spring'-,v

, which states how much power is to be expended to compress a helical spring, or generally speaking a resilient element or body, for instance a-certain distance. The greater striking power of our improved implement is thus obtained in such a way, that during the return of the driving member towards the `driving motor and shortly before the end of this motion, a. preliminary compression is imparted to the expanded impact spring,

" having the larger spring-constant, by the re# turn motion energy of the hammer head, which energy is utilized during the next forward stroke of the driving member in the direction of the blow of the hammer head,

The spring-constants of the two systems -of springs are preferably so chosen, that the amount of energy, which can be absorbed by the springrarranged at the striking end of the hammer head is substantially equal to that,

which results as the sum of the energy, which can be taken up by the spring at the freely swinging end of the hammer head and of the rebound energy existing in the hammer after the blow.

Our invention is illustrated in the accompanying drawings in which Fig. l shows in longitudinal section a portable electro-mechanical hammer in which the hammer head is joined to a reciprocating slide-like driving member by two helical springs.

Fig. 2 shows in similar section the hammer head of an electro-pneumatic hammer, which at its upper end is designed as piston adapted to slide in the cylindrical interior of the driving member, air spaces provided above and below the piston acting as air buffers,

F i g. 3 shows a longitudinal section at right angles to Fig. 2,

Fig. 4 shows a transverse section of Fig. 3 on the line 4-4 in Fig. 3,

Fig. 5 shows a longitudinal section through an electro-mechanical hammer with a device for regulating the power of the blow,

Fig. 6 shows a side elevation of Fig. 5,

Fig. 7 shows in longitudinal section a portable electro-mechanical hammer with a cooling device for discharging the heat generated more particularly by the impact,

Fig. 8 shows a modified cooling arrangement,

ing arrangement, and

Fig. 10 shows a longitudinal section through a hammer the reciprocating or oscillating driving member of which is operated by means of electro-magnets. i

Referring to Fig. 1 of the drawings, it will be observed that at the upper end of the case or housing 11 of the hammer is accommodated the electric motor 12 upon the extended shaft of which is mounted a small bevel wheel 13, which drives the large bevel wheel 14, on the face of which is provided a crankpin 15 upon which is pivoted the connecting rod 16. This rod is connected to and recipro cates a slide 17 The hammer 22 is connected with the slide 17 by two springs 19 and 21. The springs abut at their outer ends against the head 23 and the rear end disc 18 of the hammer and at their inner ends against the lower end of the slide 17. The return spring 19 has a considerably smaller springconstant than the impact spring 21. When Fig. 9 shows a still further modified coolthe hammer head is moved downward it strikes the tool, for instance the chisel 24. l

The hammer operates in the following manner: when the large bevel wheel 14 is rotated by the electric motor 12 which ma equally well he replaced by a flexible sha t driven from outside, the slide 17 is reciprocated in the housing of the hammer by the crank 15 and the Connecting rod 16. When the slide moves towards the motor the return spring 19 with lower spring-constant will,

l pact spring 21.

By the following motion of the slide towards the impact side, the impact spring is further compressed, since the hammer is forced to reverse its direction of motion, and since the slide is accelerated during the first half of its downward stroke, but the hammer, due to its inertia lags behind. Shortly before the completion of the travel of the slide in the direction of the blow, which becomes slower towards the end of the stroke, the impact spring expands and imparts to the hammer head an additional acceleration in the direction of the blow. At the moment when the hammer has attained its maximum velocity, it transfers its energy of motion to the tool 24 by impact.

By the means just described a considerable increase of the striking capacity of the hammer is obtained and the reaction upon the hands of the operator considerably reduced. A particularly favorable effect may be obtained with the striking implement by supporting the hammer axially movable only at or in the reciprocating driving member and in such a manner, that it need not be guided at any other point by any other part of the device. The advantage of this arrangement resides in the fact thatl in this way the bearing friction of the hammer is reduced to a minimum. The improved striking implement consequently possesses a very high efficiency.

A modication of the previously described two resilient elements consists in connecting the hammer with the reciprocating driving member by air cushions of diii'erent compressibility. This' pneumatic arrangement has the advantage that no gradual slackening occurs in the resiliency as happens in the case of metallic springs through fatigueafter' a certain time.

In order that the compression of the air cushions may take place as a linear function of the load, as in the case of metallic springs, air outlet nozzles are provided in the air cylinders in the direction of the length and which are of such dimensions that they become smaller with the decreasing air space in the cylinder. ln many cases it will sutiice, if one connection of the hammer with the driving member consists of an air cushion and the other of a metallic spring.

f An embodiment of this kind is illustrated in the Figs. 2 to 4 of the drawings.

Referring to these figures 25 is the case or housing of the striking implement. At the top of `this case is mounted a bearing 26 in which is journaled the driving shaft 27, which may be rotated in any suitable manner. The. rotation of this shaft is transmitted to the slide 3() by the crank 28 and the connecting rod 29, the slide being thus reciprocated within the case. rIhe slide 30 is designed as hollow cylinder. 31 is the hammer head at the top of which is located a piston 32, which is guided in 'the hollow cylinder of the slide 30 and has almost the same diameter as this hollow cylinder. The hammer head 31 projects beyond the lower wall of the hollow cylinder, in the manner of a piston rod'. The piston 32 has such a length relativelyto its cylinder that air spaces remain above and below it, which act as cushions and thus enable the piston 32 and consequently also the hammer head 31 to perform a free swinging lnotion during the reciprocation of the slide 30, the stroke of which is greater than that of the slide 30. The two air cushions above and below the piston 32 thus form an elastic connection between the hammer head 31 and the reciprocating slide 30. At the lower end of the case 25 is located the chisel 33 aga-inst which the hammer head strikes a blow during each reciprocation.

In order to render the air cushions compressible t0 a diii'erent degree slits 34 are provided in the wall portion of the slide 30 surrounding the upper air cushion and in the part surrounding the lower air cushion slits 35 are provided through which the air is able to escape from the lower air cushion into the lateral discharge ducts 36 provided in the case 25.

The air discharge slits, for instance V- shaped, 34 and 35 are so designed that they become smaller, when they are covered by the piston, at the rate at whi'ch the air space becomes smaller. The slits 34 are furthermore dimensioned in relation to the slits 35 in such a manner that the upper air cushion possesses lower compressibility, respectively is stiffer than the lower one, and would in this respect correspond withthe stiffer spring 21 of Fig. 1, and would have the same function of the latter, namely to act during the blow stroke of the hammer.

For regulating the power of the blow,

openings may bey rovided in the casin at both stroke ends o the hammer head an be placed in communication with each other by a duct or channel which is closed bya. .valve controlled from the switch for the working current in such a manner, that the air compressed by the hammer head can flow through the duct and expand also when the valve is open. The valve is preferablymechanically p coupled with the lever of the switch for the 1 driving motor by means of a connecting rod. The arrangement may be such 'that a spring engages the connecting rod and closes the valve in the state of rest and when'the switch is closed. A striking implement equipped in this way has the advantage, that its capacity may be regulated without making a change in vthe electrical part.

Anembodiment of this part of our invention is illustrated in Figs. 5 and 6, in section and side-elevation. In casing 37 is housed the driving motor 38, respectively which drives the slide 41 by means of the bevel gear 39 and the connecting rod40. The hammer 43 is connected with the slide 41 by the return spring 42` and the impact spring 45.

Return spring 42 is arranged between the springabutment disc 46 at the rear hammer end and the bottom of the slide 41, and impact spring 46 is arranged between the lower face 44 of the slide and the abutment disc 47 at the hammer head. The hammer 43 acts directly upon the chisel 49 and is designed as piston, which closely fits with its disc 47 the inside of the cylindrical hammer casing 37, so that it compresses the air above the casing end 48. The compressed air is able t0 enter the upward directed duct 51 through an opening 50 in the cylinder wall and flows through the opening 52, as well as throu h` the openings provided in the slide, into t e upper larger part of the hammer casing, where it expands again. In the duct 51 is located a cock 53 on the cone of whichl'is mounted the crank arm 54, which is connected with the lever 56 of the switch 58, mounted in the handle 57 of the hammer, by a connecting rod 55. This cock 53 is kept in the closed positon by the spring 59.

The hammer with its tool is placed on the work and the driving motor 38 is started by depressing the lever 56, whereby the hammer 43 freely oscillates in the slide 41 and exerts blows against tool 49. By the large number of blows the air contained between the striker head 48 and the hammer 43 is compressed because the cock 53 is still closed. The descent of the hammer 43 is thus damped, so that it cannotact upon the tool 49 with its f ull force. When the tool is in the proper position the cock 53 can be gradually opened by a further depression of the switch lever 56 and thus the force of the blow be increased.

If the air in the upper chambers of the hammer casing is not sufficiently expanded,

the air can be released into the open, preferably by a valve or the like arranged in the switch box 37. Since, however, the hammer casing is filled with oil to obtain good lubrication, a specially designed valve must be provided for the discharge of the air into the open, which prevents the simultaneous escape of the oil.

Toenable our improved implement to be used for long periods, it is advisable to provide special cooling devices, which prevent excessive heating of the implement, which is caused mainly by the heat developed by the rapid succession of blows. The impact heat lnay be dissipated in a particularly favorable manner by currents of air set up by the reciprocating or revolving parts of the implement. For this purpose the parts reciprocating in the implement casing are provided with openings for the passage of currents of air, and one of these parts, either the hammer or the slide transmitting the motion to the hammer, is designed as piston which draws the air in and forces it through the casmg, the air being conducted to the striking of the hammer head through openings in the reciprocating parts to carry away the impact heat generated here.

Various designs of cooling arrangements are illustrated in Figs. 7 to 9. Like parts are indlcated by like numerals of reference in all these figures.

Referring to Fig. 7, in the upper end of the case 60 of a striking hammer is housed an electrlc motor 61, which drives the slide by way of the bevel gear 62 and the eccenltrically pivoted connecting rod 64. The hammer head 72 is connected with the slide 65 by means of the springs 67 and 69, which are maintained in position by the hollow cylinder s 68 and 70 each having one of its ends deslgned as spring supporting plates. The hammer head 72 is designed as piston and provided with ducts 73, which are controlled by check valve 74. The ducts 73 are led around the striking head 75 of the hammer head, so that through the openings 77 at the lower end of the hammer case, which are likewise controlled by check valves 76, cooling air is drawn 1n during the ascent of the hammer ,and led closely past the striking head. The

heat generated there by the previous impact can thus efficiently be dissipated by the cooling current of air. The cooling air issuing on the descent in the direction of the arrows from the ducts 73 of the hammer head, ascends partly within the hollow cylinder and enters the compartment housing of the gear 62 throughthe central hollow portion in the slide 65. The other part of the cooling air Hows through the openings 71 provided in the hollow cylinder 68 and sweeps along the inner wall of the hammer case 60 until it also reaches the chamber of the gear 62 through openings 66 provided in the slide 65.

A mer head strikes the tool, such as the chisel 78.

drawn in from outside by the ascending hain-.

mer head 72 is controlled by valves 79 arranged upon the slide 65.

In the design illustrated in Fig. 9 the cooling current of air is set up by a fan 80 mounted upon the shaft of the electric motor 61. This fan draws air from outside through the openings 77 at the lower end ot the hammer case 6l, the openings 73 in the hammer head 72, the openings 66 in the slide 65 and through the openings 82 in the partition wall arranged in the upper part oi' the hammer case and forces it through the openings 83 outward. Owing to the uniformity of the current of air set up by the fan 80 no valve is necessary either in the reciprocating parts on in the lower end of the hammer provided with openings.

Instead of drawing the air in at the lower end of the hammer case, it may be conducted in the reverse direction, so that the striking end of the implement is cooled by the compressed airgenerated by the moving. parts. In consequence of the efficient discharge of the heat of impact attained by our invention, the striking capacity of the hammer may be considerably increased, particularly in continuous operation.

Our invention is equally well applicable to blow lstriking implements and hammers in which the hammer head is connected with the axially movable core of electro-magnets or solenoids.

Generally in electro-magnetically operated devices a plurality of electro-magnets are used, the common core of which serves as drive. Such known hammer-type implements may be operated with direct or alternating current, the solenoids being alternately energized. These implements are connected with alternating current mains in known manner referably across rectiiiers or electron tubes by which each solenoid receives a current impulse of constant polarity. The number of blows of this implement corresponds with the frequency of the alternating current; when connected to a 50 cycle alternating current supply such an implement will thus strike 3000 blows per minute. The capacity of the implement depends upon the mass and the speed. Since the dynamic energy grows with the square of the velocity, the capacity of the implement may at equal mass be considerably increased, if it were possible to increase the speed of the implement in any way. A particularly good effect may in such implements be obtained by interposing between the hammer head and the magnet core springs of different springconstants, the spring of high spring-constant being arrangedin such a way, that it imparts to the hammer head an additional acceleration in the direction of the blow.

An embodiment of/our invention applied to such a hammer is illustrated in Fig, 10.

Referrin0r to Fig. 10, the hammer head 101 is arrangedacO-axially with the magnet core 99 and connected with it by the two inter-- posed springs 102 and 103. In the hammer casing 96 are located the two magnet coils 97 and 98 within and between which is movably disposed the cylindrical iron core 99 provided with a bore. 104. In the bore 104 of the core is guided the rod 100,*which at its lower end carries the hammer head 101 and at its upper end the spring abutment plate 105. Between the plate 105 and the core 99 is arranged the helical spring 102 and between the hammer head 101 and the core 99 the helical spring 103, the spring-constant of which is greater than that of the spring 102.

.In the striking end 106 of the'casing is inserted the chisel 107 upon which acts the hammer head 101.

When the solenoid 97 is energized the core 99 is moved upward, whereby the return spring 102 is compressed and the impact spring 103 expanded. Shortly before the completion of the ascent of the core 99 the return spring 102 expands during the motion of the hammer head and imparts to the hammer head an additional upward acceleration. By this acceleration of the hammer head a cer tain preliminary compression is imparted to the impact spring 103. By excitation of the magnet solenoid 9S the core 99 is moved towards the striking side, whereby the impact spring is further compressed and simultaneously the hammer head forced to reverse its direction of travel. Shortly before the completion of the descent of the core 99 in the direction of the` blow, the impact spring expands and imparts an additional acceleration to the hammer head in the direction of the blow. At the moment it has attained its highest velocity, it transmits its dynamic energy to the chisel 107 by striking it a blo,w. The velocity of the hammer head is therefore at the end of the stroke considerably greater than that of the core 99. The two springs also reduce considerably the reaction of the blows on the hands of the operator.

In order to keep the weight of the implement as low as possible, it is advisable to construct the casing not of iron, but of a material of lower density, such as a light metal. For the same reason the core 99 located between the solenoids may also be made of a material of lower density. In such a case it must be provided with insertions of iron at the places which carry the strongest magnetic flux.

Various modifications and changes may be made without departing from the spirit and the scope of the invention, and we desire,

therefore, that only such limitations shall be placed thereon as are imposed by the prior I art.

We claim as our invention:

1. A blow striking implement comprising in combination a casing, a hammer driving element slidingly mounted in said casing, means for operating said driving element, a

hammer disposed' in said casing to move 10ned to be reciprocated. by said driving motor,

an elongated hammer disposed in said casing to move longitudinally with respect to said driving member, and two opposingly arranged systems of springs for connecting the two ends of said hammer with said driving member, the spring constants of said systems of springs being different fromeach other.

3. A blow striking implement.comprising in combination, a casing, a driving motor in said casing, a driving member slidiiigly disposed in said casing and adapted to be recip-l rocated by said driving motor, an elongated hammer disposed in said casing. to move longitudinally with respect to said driving mem` ber, and two opposingly arranged systems of springs of diiferentspring constants for connecting the two ends of said hammer with said lriving member, the spring at the striking end having a large spring consta-nt, and the spring at the rear end of the hammer having a small spring constant.

4. A blow striking implement comprising in combination, a casing, a driving motor mounted in said casing, a hand switch for controlling said motor, a driving member slidin ly disposed in `said casing and adapted to e reciprocated by said driving motor, an elongated hammer having one end formed as a piston shaped head and being slidingly disposed in said casing and in said driving member, two opposingly arranged systems ofV springs for connecting the two ends of said hammer with said driving member, the springconstants of said systems of springs being different, and means for regulating the power of the blow, consisting of two ports in the Wall of the casing provided at the ends of the stroke path of said hammer, a duct connecting said ports and a valve in said duct controlled by the movements of said switch for controlling the 'displacement of air between the underside and upper side of the hammer head.

5. A blow striking implement comprising in combination, a casing, a drivin motor mounted in said casing, a hand switch for controlling said motor, a driving member slidingly disposed in said casing and'adapted to be reciprocated by said driving motor, an elongated hammer having one end formed as a piston shaped head and being slidingly disposed in said casing and in said driving member, two opposingly arranged systems of springs for connecting the two ends of said hammer with said driving member, the spring constants of said systems of springs being different, and means for regulating the power of the blow, consisting of two ports in the wall of the casing provided at the ends of the stroke path of said hammer, a

i duct connecting said ports and a valve in said duct for controlling the displacement of air between the underside and the upper side of the hammer head, and a connecting rod for mechanically coupling said valve with said switch for the purpose described.

6. A blow striking implement comprising in combination, a casing, a driving motor mounted in said casing, a hand switch for controlling said motor, a driving member slidin ly disposed in said casing and adapted to e reciprocated by said drivin motor, an elongated hammer having one en formed as a piston shaped head and being slidingly disposed in said casing and in said driving member, two opposingly arranged systems of springs for connecting the two ends of said hammer with said driving member, the spring constants of said systems of springs being diierent, and means for regulating the power of the blow, consisting of two ports in the wall of the casing provided at the ends ofthe stroke path of said hammer, a duct connecting said ports and a valve in said duct for controlling the displacement of air between the underside and the up er side of the hammer head, and a connecting rod for mechanically coupling said valve with said switch for the purpose described, and a spring adapted to engage said connecting rod and to close said valve when said switch is open.

In testimony whereof we aiiix our signa- 

